5.3 Swappers; Gas Mileage, Swap Cost Total?

[Jjkage84]

Title says it all folks. Very curious about this.

Also interested in modifications required, and mechanical skill required.

I know there are a million threads between the two sites on this swap, and I'm not looking for in depth responses unless you want to go into detail. Just looking for straight shot answers.

Thanks guys/gals!

[racerx12003r1]

Well, I can tell you that a friend of mine from here has a 6.0 in his rig. With a 400 turbo and q-track, he is reportedly getting in the mid 20s per gallon. The Vortec engines can get quite good mileage. I am currently in the process of a transplant for my J-10 now. the best thing I have done so far is to pull the whole front clip off. Man, does it make it easy. Now I just have to decide if I am going to use the 350 I have for it, or the 6.0 I just got ahold of.

[Jjkage84]

Mid 20s?! Whew, that'd be sweet!

[XJChad]

I am in the middle of my swap so I dont have mpg #s. As far as cost it all depends on how in depth you want to go. Right now I am into mine for $2000 to $2500 and still have more to go. Probably another $1000. This includes my donor motor, tranny, tcase, alum radiator, fuel pump, and tank. I also went through my LS and installed a new oil pump, timing chain, knock sensors, gaskets, pcv, crank bolt, plugs, wires and powdercoated the oil pan and valve covers.
As far as difficulty, its not bad, but this depends on experience.

[Cassidy]

I wonder about claims of 20+ mpg with this combo I have a 2005 gmc yukon with 80 thousand miles completely stock well maintained no big tires or anything and it gets 14 to 15 mpg....5.3 overdrive trans awd

[Jjkage84]

I had an 01 suburban that I could get around 16.5-17 Hwy. I don't know about mid 20's, but I could see a bit better than my big Ole suburban. But who knows.

I could deal with 16.5+ mpg on Hwy as long as it was then key reliable. That's more so what I want with the swap.

[Cassidy]

Ohhhhhhh I'm sure under the right conditions I could get 20 in my yukon ....downhill with a tailwind. ..... don't get me wrong a 5.3 swap especially with an overdrive trans would be awesome and make the jeep more enjoyable to drive. I just think you would be lucky to get 2 mpg better than an amc 360 tbi setup.. now engine lifespan on the 5.3 or any modern engine is probably much better.

[XJChad]

I had a 99 Chevy Z71 extended cab with a fiberglass topper and routinely got 21 to 22mpg on the highway and 14 to 16 in town. I would get about 14mpg on the hwy when towing my lifted XJ on a 16ft dovetail. The truck was all stock. I also noticed an improvement when I switched to Amsoil synthetic oil.

[COLORADOCRAWLER]

Currently I am only getting around 13 in town and 16.5 Highway, but.....that is driving 75 to 85 on the highway and I have stock 2.72 axle gears thus rendering overdrive practically useless, unless you want to run right at 80 on relatively flat road. Any faster or any grade to the road and the drag becomes so great that it downshifts and any slower it starts to lug a little and also downshifts. Most of the time I just run 75-80 in drive and the RPMs are fine. I should also mention though that I frequently try to mash the fun pedal through the floorboard In town soooo...can't wait to see how much torque and gas milage I can recover with the proper gears and a useable overdrive on the highway.

As far as costs, I kept a detailed spreadsheet of everything, to include fluids and expendables/hardware and it came out to about $6500 without A/C. You can certainly do this a little cheaper with used fuel system parts and hacking the harness yourself, but time is money and you can't put a price on your own sanity. I did hit the easy button and use some Dakota Digital and Lokar products, which could be done other ways with much more difficulty, but holy crap that was money well spent. I also bought a used harness from a guy out of New York who hacked it up for me and made it stand alone $350 total, again $ well spent. The engine tranny combo had approx. 90K on them and the junkyard NP241 has unknown miles but is in good shape. I definately have plenty of salvage parts in the mix but went with new sensors, fuel system parts, and other small parts when practical to do so.

Only problems I had were two mixed up wires that I had to find (my fault), and after sittimg for 8 years in my garage the fuel rails needed flushed and injectors cleaned, water pump had a little seep and was replaced and alternator had a rough bearing so I replaced it. I will have nearly 20K miles on this set up by Thanksgiving (1yr) and this swap rules. Despite past auto projects, I consider the 5.3 swap my opus. It incorporaed all of the various systems skills mechanical/electrical/fuel/ect. The reliability and no leaks factors alone are worth the effort as well as the additional power and smooth delivery. Hope that helps.

[Jjkage84]

Awesome! It's definitely something I'm going to do if I decide to keep this particular FSJ, or any new one I get.

I guess I may not mind it so much once I get all the vacuum leaks, Exhaust, ect fixed. It doesn't "run" the way I I remember my 68 Chevy truck did and it had a carb blah blah blah. Just need to get everything in check and I won't mind it so much

[XJChad]

Crawler, what size tire & lift (if any) are you running? Mine is also a 2.72 stock gear and Im debating on a 32" tire. I have the 4" Rustys installed and a used set of 33's but will be going smaller when I buy new tires. Also what gear ratio are you going to step up to?

I am going to pay someone to do the harness as well. After making my own mounts I decided I will pay for the wiring to save my sanity.

[COLORADOCRAWLER]

Crawler, what size tire & lift (if any) are you running? Mine is also a 2.72 stock gear and Im debating on a 32" tire. I have the 4" Rustys installed and a used set of 33's but will be going smaller when I buy new tires. Also what gear ratio are you going to step up to?

I am going to pay someone to do the harness as well. After making my own mounts I decided I will pay for the wiring to save my sanity.

Currently I have 31x 10.50s on there and I believe a 2.5" lift (previous owner installed). I will be stepping up to 33s and 4.10 gears in the future. I will say that I would not go with any bigger tires than 31s without regearing. Think it would be too hard on the tranny and would lug the motor a little too much, just my .02 pesos.

[XJChad]

Ok thanks for the advice. I plan on towing a couple ATVs as well so I will definately get a gear swap lined up.